ClosedXML/ClosedXML/Excel/CalcEngine/Functions/Information.cs

using ClosedXML.Excel.CalcEngine.Exceptions;
using System;
using System.Collections.Generic;
using System.Globalization;

namespace ClosedXML.Excel.CalcEngine.Functions
{
    internal static class Information
    {
        public static void Register(CalcEngine ce)
        {
            //TODO: Add documentation
            ce.RegisterFunction("ERRORTYPE", 1, ErrorType);
            ce.RegisterFunction("ISBLANK", 1, int.MaxValue, IsBlank);
            ce.RegisterFunction("ISERR", 1, int.MaxValue, IsErr);
            ce.RegisterFunction("ISERROR", 1, int.MaxValue, IsError);
            ce.RegisterFunction("ISEVEN", 1, IsEven);
            ce.RegisterFunction("ISLOGICAL", 1, int.MaxValue, IsLogical);
            ce.RegisterFunction("ISNA", 1, int.MaxValue, IsNa);
            ce.RegisterFunction("ISNONTEXT", 1, int.MaxValue, IsNonText);
            ce.RegisterFunction("ISNUMBER", 1, int.MaxValue, IsNumber);
            ce.RegisterFunction("ISODD", 1, IsOdd);
            ce.RegisterFunction("ISREF", 1, int.MaxValue, IsRef);
            ce.RegisterFunction("ISTEXT", 1, int.MaxValue, IsText);
            ce.RegisterFunction("N", 1, N);
            ce.RegisterFunction("NA", 0, NA);
            ce.RegisterFunction("TYPE", 1, Type);
        }

        static IDictionary<ErrorExpression.ExpressionErrorType, int> errorTypes = new Dictionary<ErrorExpression.ExpressionErrorType, int>()
        {
            [ErrorExpression.ExpressionErrorType.NullValue] = 1,
            [ErrorExpression.ExpressionErrorType.DivisionByZero] = 2,
            [ErrorExpression.ExpressionErrorType.CellValue] = 3,
            [ErrorExpression.ExpressionErrorType.CellReference] = 4,
            [ErrorExpression.ExpressionErrorType.NameNotRecognized] = 5,
            [ErrorExpression.ExpressionErrorType.NumberInvalid] = 6,
            [ErrorExpression.ExpressionErrorType.NoValueAvailable] = 7
        };

        static object ErrorType(List<Expression> p)
        {
            var v = p[0].Evaluate();

            if (v is ErrorExpression.ExpressionErrorType)
                return errorTypes[(ErrorExpression.ExpressionErrorType)v];
            else
                throw new NoValueAvailableException();
        }

        static object IsBlank(List<Expression> p)
        {
            var v = (string) p[0];
            var isBlank = string.IsNullOrEmpty(v);


            if (isBlank && p.Count > 1) {
                var sublist = p.GetRange(1, p.Count);
                isBlank = (bool)IsBlank(sublist);
            }

            return isBlank;
        }

        static object IsErr(List<Expression> p)
        {
            var v = p[0].Evaluate();

            return v is ErrorExpression.ExpressionErrorType
                && ((ErrorExpression.ExpressionErrorType)v) != ErrorExpression.ExpressionErrorType.NoValueAvailable;
        }

        static object IsError(List<Expression> p)
        {
            var v = p[0].Evaluate();

            return v is ErrorExpression.ExpressionErrorType;
        }

        static object IsEven(List<Expression> p)
        {
            var v = p[0].Evaluate();
            if (v is double)
            {
                return Math.Abs((double) v%2) < 1;
            }
            //TODO: Error Exceptions
            throw new ArgumentException("Expression doesn't evaluate to double");
        }

        static object IsLogical(List<Expression> p)
        {
            var v = p[0].Evaluate();
            var isLogical = v is bool;

            if (isLogical && p.Count > 1)
            {
                var sublist = p.GetRange(1, p.Count);
                isLogical = (bool) IsLogical(sublist);
            }

            return isLogical;
        }

        static object IsNa(List<Expression> p)
        {
            var v = p[0].Evaluate();

            return v is ErrorExpression.ExpressionErrorType
                && ((ErrorExpression.ExpressionErrorType)v) == ErrorExpression.ExpressionErrorType.NoValueAvailable;
        }

        static object IsNonText(List<Expression> p)
        {
            return !(bool) IsText(p);
        }

        static object IsNumber(List<Expression> p)
        {
            var v = p[0].Evaluate();

            var isNumber = v is double; //Normal number formatting
            if (!isNumber)
            {
                isNumber = v is DateTime; //Handle DateTime Format
            }
            if (!isNumber)
            {
                //Handle Number Styles
                try
                {
                    var stringValue = (string) v;
                    return double.TryParse(stringValue.TrimEnd('%', ' '), NumberStyles.Any, null, out double dv);
                }
                catch (Exception)
                {
                    isNumber = false;
                }
            }

            if (isNumber && p.Count > 1)
            {
                var sublist = p.GetRange(1, p.Count);
                isNumber = (bool)IsNumber(sublist);
            }

            return isNumber;
        }

        static object IsOdd(List<Expression> p)
        {
            return !(bool) IsEven(p);
        }

        static object IsRef(List<Expression> p)
        {
            var oe = p[0] as XObjectExpression;
            if (oe == null)
                return false;

            var crr = oe.Value as CellRangeReference;

            return crr != null;
        }

        static object IsText(List<Expression> p)
        {
            //Evaluate Expressions
            var isText = !(bool) IsBlank(p);
            if (isText)
            {
                isText = !(bool) IsNumber(p);
            }
            if (isText)
            {
                isText = !(bool) IsLogical(p);
            }
            return isText;
        }

        static object N(List<Expression> p)
        {
            return (double) p[0];
        }

        static object NA(List<Expression> p)
        {
            return ErrorExpression.ExpressionErrorType.NoValueAvailable;
        }

        static object Type(List<Expression> p)
        {
            if ((bool) IsNumber(p))
            {
                return 1;
            }
            if ((bool) IsText(p))
            {
                return 2;
            }
            if ((bool) IsLogical(p))
            {
                return 4;
            }
            if ((bool) IsError(p))
            {
                return 16;
            }
            if(p.Count > 1)
            {
                return 64;
            }
            return null;
        }
    }
}